1. Field of the Invention
The present invention relates to organizing networks having a number of nodes, such as but not limited to wireless sensors, configured to electronically communicate information.
2. Background Art
One of the main power costs in wireless sensor networks or other networks is energy consumption associated with an active/powered radio receiver/transceiver used to facilitate nodal communications. In order to prolong battery life and otherwise limit power consumption, it can be advantageous to minimize an amount of time that the receiver is active, i.e., to reduce the window in which it listens for and/or communicates information.
In order to minimize this so called communication window, each node may be configured to listen (be active) for a period of time and to be turned off (inactive) for another period of time. Energy saving increases as the inactivity period increases. Because each node typically relies on communicates from the other nodes for processing and other operations, the period for which each is active and inactive may be synchronized so that nodes all are listening for the same period of time and inactive for the same period.
Beaconing is one process for synchronizing nodal communications in which nodal activity states are coordinated. Beaconing generally relates to activating each node to listen and communicate during a beaconing window and to deactivate during a period of time outside of the beaconing window. To limit communication collisions and otherwise facilitate communications, each node may be assigned its own time slot within the window in which they are to transmit data packets, if the transmission of data packets is desired. Each node, therefore, listens to the packets communicated from the others within beaconing window, and transmits without fear of collision.
Current approaches to establishing the beaconing window rely on a centralized coordinator that defines when the listening window starts and ends, and assigns all the other nodes a slot in which to transmit. If the centralized coordinator node were to fail, new nodes arriving cannot be assigned a slot, and in many schemes even the existing nodes would become lost, as the start of each window may be marked by the coordinator. This is problematic. If the coordinator is lost or unavailable, the nodes essentially form a collection of peer nodes that must then include capabilities to detect coordinator presence and capabilities to facilitate mutually determining and selecting a common coordinator, adding extra complexity and costs. The coordinator is a single point of failure and maintaining such a coordinator can add complexity cost to the designing and supporting such a network.